I have heard from many GC's, owners and installers: The moisture vapor emission rate (MVER) is pretty low, let's use that number and forget about the rH test!

Sometimes I like to answer with a shocking statement to derail their train of logic. I tell them water isn't the problem! We have hundreds of wonderful waterproof glues. Water isn't the issue!

This statement grabs their attention (well why in the world are we measuring moisture then?? ) and lets me explain further. The concrete slab is a reservoir of alkalinity and salts and moisture that can destroy a glue, even destroy a concrete slab sometimes. What we have found after many years of CaCl testing is that we can get a low MVER reading but still have this highly active concrete slab under the surface just waiting to destroy our floor covering.

RH testing looks inside the concrete to determine the potential a slab has to ever be problematic. If we find a low rH reading, this means the slab has completed most, if not all, of its hydration, the water of convenience is nearly gone, and the potential for future problems is greatly reduced.

More manufacturers are embracing the rH testing method in the US because they have witnessed the faulty logic of MVER testing and may have even had failures on slabs that passed the CaCl test. Recently the ASTM committee for calcium chloride testing (ASTM F-1869) changed the method of test installation intending to create a more open and porous surface of the concrete slab which should result in higher MVER readings compared to the previous test protocol.

The problem I have is nobody has acknowledged the elephant in the room. The CaCl test has no real pedigree, what we thought was a good number according to last year's test (3 lbs / 5lbs) was resulting in failures, now the MVER numbers are coming back higher, is 3lbs still a good number? It wasn't working before, will it work now? When we grind the test site, we alter the surface of the slab. Do we need to alter the entire slab to expect similar conditions before installation?

RH testing reads inside the slab. It was designed to indicate a concrete slab's potential for failure based on the moisture inside. The readings are accurate, stable and dependable, but most of all the readings work. The science behind them is solid. You can trust that a properly conducted rH test will give results you can bet your flooring on, and stake your reputation on.

As for all those CaCl test kits you have left over? Send them up north to me, I use them as sidewalk de-icer in the winter.

JD, your beginning to sound like the guy in the orange shirt. I kid, I kid!! But you, you talk in circles. First you speak of MVER, then jump to water and back to moisture??? How is water MVER?

Actually ASTM F-1869 has said to lightly grind the surface for awhile now.. I think, hey is that as bad a drilling a hole in the slab looking for....... ?

So, tell me how long does it take the moisture vapor to move from the 40% level in a 4 inch slab to top and then out the top depending on surface openness? How about one inch? How much difference is one inch depth to 1.6 inches? That much? They say a cacl test only to one inch and on a 4 inch slab why would there be so a discrepancy in numbers?

Tell ya what, when all these experts put there money where their mouth is and guarantees the floor when tested with their infallible device I will buy into that.

Now when testing with in situ we are testing for hidden rh down in the slab, right? So if there is excessive rh down in the slab and equilibrates to the surface what does it do that is bad for floorcovering? Make the surface highly alkaline? Is it the pressure only or does it create high mver? If high mver then why not test for mver? Or are we testing for alkalinity or

I think you have found your calling. You should write articles for the flooring trade magazines.

(07-19-2012, 12:40 PM)Ernesto Wrote: JD, your beginning to sound like the guy in the orange shirt. I kid, I kid!! But you, you talk in circles. First you speak of MVER, then jump to water and back to moisture??? How is water MVER?

Water isn't MVER, but without water there would be no moisture emission now would there? So when you test for moisture emission, what do you know? Just about nothing. You have no idea what the slab is like, you don't know the potential for problems down the road. I can tell you I have seen many projects with MVER readings below 3lbs/1000/24 fail, but I have never seen a failure with a slab at 75%rH.

Actually ASTM F-1869 has said to lightly grind the surface for awhile now.. I think, hey is that as bad a drilling a hole in the slab looking for....... ? I have the ASTM dating back many many revisions and I have never read where it says you should lightly grind the surface. Please post that quote here.

So, tell me how long does it take the moisture vapor to move from the 40% level in a 4 inch slab to top and then out the top depending on surface openness? How about one inch? How much difference is one inch depth to 1.6 inches? That much? They say a cacl test only to one inch and on a 4 inch slab why would there be so a discrepancy in numbers? You don't understand rH readings! The 40% depth has been shown to be the depth that represents the equilibrated rH of the slab. Manufacturers across the globe have determined that a slab that equilibrates at 75% poses very little risk for failure over the long run. (for the record, the CaCl test is only testing the very dry top 1/4" of concrete, and only if the slab is properly prepared, which I have never seen.... ever).

Tell ya what, when all these experts put there money where their mouth is and guarantees the floor when tested with their infallible device I will buy into that. I know at least one manufacturer that guarantees their flooring based on the rH reading if the readings are Wagner Rapid RH! They will ONLY recognize rH readings, they won't even let you install their floors using a CaCl test. They are also the largest rubber flooring manufacturer in the world.

Now when testing with in situ we are testing for hidden rh down in the slab, right? So if there is excessive rh down in the slab and equilibrates to the surface what does it do that is bad for floorcovering? Make the surface highly alkaline? Is it the pressure only or does it create high mver? If high mver then why not test for mver? Or are we testing for alkalinity or The rH isn't hidden, it's just where it always is. The multitude of failing slabs that read perfectly fine using CaCl has lead us to find a new and better measuring stick for concrete readiness.
High slab rH indicates the potential for failure. It could be alkalinity that eats your glue, it could be osmotic blisters. It could be ASR destroying your slab! High moisture slabs are a ticking time bomb. The point is you won't have any of these issues with a 75% rH slab, but we have seen thousands of these problems with slabs that passed the CaCl test.

I think you have found your calling. You should write articles for the flooring trade magazines.

I know.... There is a gap in the knowledge concerning concrete and flooring and I am spreading the word.

Second, I have heard various opinions as to what a CaCl test reads to depth wise. I think your wrong about the 1/4. When ever in a debate, change the rules. ha ha

Third, you say,

Quote:I can tell you I have seen many projects with MVER readings below 3lbs/1000/24 fail, but I have never seen a failure with a slab at 75%rH.

Then you say,

Quote:and only if the slab is properly prepared, which I have never seen.... ever).

Your contradicting yourself again. So, I take it then you have never seen a functioning floor, cacl tested properly prepared and the floor has having had zero problems. Why, because there are probably tens of millions of them you have never seen because people do not report jobs that have not failed. lol So perhaps if one only properly prepared the substrate you would not have a failure.

As far as the manufacturers warrantying the floor, I mean the people who make the rh testing devices. If your going to ballyhoo your product as invincible then put your money where your mouth is and offer to buy that floor if it fails. properly prepared and tested of course.

Ahhhh... But remember, I was the QC guy at a company that built clinics and hospitals. I have seen thousands and thousands of functioning floors.
I've seen some that should have failed but they held somehow. I've seen some installed so poorly I would have bet any amount of money they would fail quickly but they didn't. I've torn apart working floors and failed floors, and tested them in every kind of way you can imagine.

You want the RH equipment manufacturer to pay for a floor failure? Why would you expect that? They don't tell you what RH you need to install a floor, the flooring and adhesive manufacturers do that.

I'm saying I have never seen a floor at 75% or less RH fail due to moisture or alkalinity. I have seen failures due to improper installation on a perfectly fine slab though.

(07-12-2012, 01:04 PM)eaadams Wrote: Yes there really is a gap in the concrete knowledge on this subject. I used to think the RH Hood method would help alleviate this but it hasn't.

I'd love to see a study on RH Hood tests done next to CaCl to see if there is any parallel.

Hoods are just so expensive... I put those GE probes in mine and they are guaranteed targets for lifts.

That would be interesting. I did side-by-side tests with a hood and RH @depth and the hood readings went UP past 72 hours.

I don't know if this is relevant but 1869 calls for light grinding of the surface, whereas the hood method 2420 calls only for "clean, bare concrete", and later says "considerable amount of additional time may be required for the satisfactory performance of the test because of low porosity surface...". I wonder if requiring a light surface grind for the hood might be a better idea.

F2420 has just been approved (published last month) for inclusion in our resilient flooring standard- but only where in-situ cannot be performed where drilling is innapropriate. So there's going to be some fast learning going on...

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